Swann made his WWE debut at an NXT house show on October 30, 2015, wrestling in a Halloween battle royal, which was won by Bayley. Swann made his singles match debut at a house show on November 20, losing to Riddick Moss. He made his first televised appearance on the January 20, 2016 episode of NXT, losing to Baron Corbin. On the March 23 episode of NXT, Swann was defeated by NXT Champion Finn Bálor. On October 13, Swann and No Way Jose entered the 2016 Dusty Rhodes Tag Team Classic, defeating Drew Gulak and Tony Nese in their first round match. They were eliminated from the tournament on October 28 by The Authors of Pain (Akam and Rezar).
On June 13, 2016, Swann was announced as a participant in the upcoming Cruiserweight Classic tournament. The tournament began on June 23 with Swann defeating Jason Lee in his first round match. On July 14, Swann defeated Lince Dorado in his second round match. On August 26, Swann was eliminated from the tournament in the quarterfinals by eventual winner T.J. Perkins.
On the August 22 episode of Raw, Swann was announced as part of the upcoming cruiserweight division. Swann made his Raw debut on September 19, wrestling in a four-way match won by Brian Kendrick and also included Cedric Alexander and Gran Metalik. On the November 21 Raw, Swann defeated Noam Dar and T.J. Perkins to become the number one contender to the WWE Cruiserweight Championship. On November 29, Swann defeated Brian Kendrick on the premiere episode of 205 Live to win the title. The following week, Swann defeated Kendrick in a rematch to retain the title, following a distraction from Perkins. On December 18 at Roadblock: End of the Line, Swann retained the title in a triple threat match against Kendrick and Perkins. After the match, Swann and Perkins were attacked by a returning Neville. On January 29, 2017, Swann lost the Cruiserweight Championship to Neville at the Royal Rumble. After recovering from a minor injury, Swann received his title rematch against Neville on the March 6 Raw, but again lost.
On December 10, 2017, WWE suspended Swann indefinitely for violating the company's zero tolerance policy. He was originally scheduled to face Drew Gulak in a match to determine the number one contender to the Cruiserweight Championship, (which was then held by Enzo Amore), the following night on Raw, but the match was cancelled. On February 15, 2018, WWE officially announced that Swann and WWE had mutually agreed on his release.